File:General physiology of muscles and nerves (1881) (14797515463).jpg

Identifier: generalphysiolo00rose (find matches)
Title: General physiology of muscles and nerves
Year: 1881 (1880s)
Authors: Rosenthal, I. (Isidor), 1836-1915
Subjects: Physiology Muscles Nerves
Publisher: New York, D. Appleton and company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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the muscle. On the fore-end of the leverare two screws 2^ and q, the former of which ends belowin a platinum point resting upon a platinum plate,while the latter is extended into a point of copper-amalgam, immersed in a capsule of quicksilver. Theplatinum plate and the capsule of quicksilver are iso-lated from the stage and from each other, the latterbeing conduc^ively connected with the vice k, the formerwith /v/. If the current which is to act on the swinging mag-net is inserted between h and k, it passes through thequicksilver capsule, through the portion of the lever be-tween 2^ and q, through the platinum plate, &c., as longas the muscle does not contract. As soon, however, asthe muscle contracts, it interrupts the current betweenp and the platinum plate. If the apparatus is so ar-ranged that the current is closed at the moment atwhich any irritant affects the muscle, then this currentwill circulate until the muscle, in contracting, again 60 PHYSIOLOGY OF MUSCLES AND NERVES.
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Fig. 20. ArrARATus for measitrtng the dui;atton of siuscle- CONTRACTIOX. MEASUREMENT OF PULSATION BY ELECTRICITY. 61 interrupts the current. This period, which may be cal-culated by the method described in the last paragraph,represents exactly that which elapses from the momentat which the irritant affects the muscle to that at whichcontraction begins. Yet another cucmnstance must be taken into con-sideration, in order to render actual measurements pos-sible. The muscle contracts on being irritated. Thiscontraction, however, lasts only a very few parts of asecond, and the muscle then resumes its former length.In the experiment justdescribed, the currentinterrupted by the con-traction of the musclewould soon be againcompleted, and the mag-net would undergo a newdeflection even beforethe first vibration wasfinished. In order toobviate this, Helmholtz ^^J^employed means the na-ture of which is madeintelligible in fig. 21. This figure represents the endof the lever of the apparatus alread

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